Welcome to part three of our Leak Inspection and Repair Blog Series that explores bathroom leaking causes and solutions. This article focuses on how to repair a bathtub overflow drain leak.

Have you recently noticed signs of water leaking in your home? Maybe you’ve realized water stains are beginning to appear on the ceiling or walls. If so, a leak might be coming from your bathtub. When left unattended, it could lead to water damage that risks spreading mold and mildew throughout your home.

To avoid costly repairs, screen for signs of bathtub leaking and identify where the problem is coming from as soon as possible. If it turns out your bathtub drain is responsible, you’ll need to determine if leaking is coming from the overflow drain (located on the wall of the tub), or the waste drain (located on the floor of the tub.)

For tips on how to repair the waste drain, check out our article 6 Steps to Eliminate Bathtub Drain Leaking. For guidance on how to address the overflow drain, continue reading for our quick and easy repair tips.

What’s Causing My Bathtub Overflow Drain Leak? 

If you find your bathtub leak is coming from the overflow drain, you’ll want to understand why it’s leaking before you can fix the problem. In most cases, damaged gaskets that help seal the overflow drain are responsible for water leaking behind the bathtub. 

The gasket is the black rubber ring that surrounds your drain hole. When the material deteriorates with age, the seal becomes compromised, causing water to leak and potentially resulting in water damage. Thankfully, in most cases, you’ll just need to replace the worn or cracked gasket.

To seal your overflow drain and prevent further leaking from damaging your home, follow our simple five-step process.

Tools You’ll Need for Sealing Bathtub Overflow Drain

If you want to try sealing your bathtub overflow drain at home, you’ll need a few basic tools:

• Utility knife/scraper
• Screwdriver
• Overflow gasket (Be aware that some Kohler overflow plates require a specific gasket fitted for the assembly.)

5-Step Guide for Sealing Bathtub Overflow Drain

After you’ve gotten your basic materials together, it’s time to get started on the repair in order to stop your bathtub overflow drain leak.

1 – Remove overflow drain plate.

If necessary, use a utility knife or scraper to remove any caulk from around the overflow drain plate.

Remove the screws that attach the overflow plate to the wall of the tub. If no screws are visible, simply pop off the plate by placing your thumbs at the bottom and gently pressing up.

If your bathtub is old, be very careful when removing the screws. They could snap, and you would need to replace the entire overflow plate assembly.

The overflow drain pipe should now be exposed. If a bracket is covering the drain opening, remove it with a screwdriver.

2 – Examine overflow pipe.

Examine the overflow pipe and make sure you’re able to move it slightly inside the drain hole. This should allow you to insert a screwdriver and carefully remove the rubber gasket from around the pipe. 

If you’re unable to remove the gasket because the pipe is too rigid, contact us or a local plumber. A plumber will likely need to replace both the gasket and part of the overflow pipe.

3 – Remove overflow gasket.

Remove the gasket by pulling it free with your hands. If necessary, use a screwdriver to move the pipe slightly, creating space between the drain and the tub as you pull it out. If it doesn’t come out by hand, a screwdriver can sometimes also be helpful to gently pry it out. 

Examine the gasket. If the gasket was dry rotted or in some other way compromised, you’ve likely discovered the source of your bathtub overflow drain leak.

Examine the circumference of the overflow pipe and clean any leftover debris from the gasket with a paper towel or rag.

4 – Replace overflow gasket.

Hold the new gasket on its side to see if it’s beveled (i.e., if one side is thicker than the other). This will help you determine how to properly install it.  

Insert the gasket, centering it in the drain hole opening. If the gasket is beveled, the thinner side of the gasket will fit around the top of the overflow drain and the thicker side around the bottom.

Work the gasket into place with your fingers, pressing around the circumference of the drain hole to create a seal. 

The gasket should be nicely seated around the circumference of the pipe and aligned with tub drain. There shouldn’t be any gaps. 

Be aware that it can take some time to properly set a gasket. Avoid using any tools or objects to help you seat the gasket. You could poke holes in the material, leaving you with a bathtub that still leaks.  

5 – Reattach overflow drain plate.

Reattach the bracket (if applicable), centering it across the drain hole and screwing it on. 

This should pull the overflow pipe forward, compressing the gasket and resulting in a water-tight seal.

Reattach overflow plate with the screwdriver, making sure the open slit on the outside of the plate is pointing down. 

This redirects excess water to the overflow drain when the water level rises to the bottom of the plate. 

Tighten the plate, being careful not to overtighten. 

After you’ve successfully resealed your overflow drain, test to see if you’ve fixed the bathtub leak by filling the tub slightly past the overflow plate and checking the location(s) you had first identified water pooling.

If leaking persists, you may need to either reseal/repair the waste drain (located on the floor of the tub) or replace the entire waste and overflow drain assembly. Because it’s usually easier to repair the waste drain (if it only needs to be resealed) rather than attempting to replace an entire drain assembly, you may want to start there.

Look out for more articles from our Leak Inspection and Repair Blog Series, which overview:

• Part 1 – 4 Main Causes of Pesky Bathtub Leaking
• Part 2 – Bathtub Drain Leaking (waste drain repair)
• Part 3 – You’re Here
• Part 4 – Shower Valve Leaking repair (for two- or three-handle valves)
• Part 5 – Leaking Shower Valve repair (for one-handle Moen fixtures)
• Part 6 – Adjusting Your Trip-lever Drain Stopper – ​​Why Your ​​Tub Doesn’t Hold Water

If you’re in need of more thorough leak detection in Montgomery County or are looking for a reliable plumber in Gaithersburg, MD or the surrounding areas, contact Heil Plumbing today.

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Heil Plumbing is a family-run company owned by a third-generation master plumber. We can help you with a full range of plumbing services in Rockville and the Baltimore-D.C. metropolitan area, including toilet installation and repair, leak detection and pipe repair, faucet repair and installation, drain cleaning, and water heater repair in Montgomery County and the surrounding areas.